Side-channel pump with asymmetrical cross-sections of the side channels

ABSTRACT

The invention relates to a side-channel pump that allows a reduced wear. The side-channel pump has a housing which encloses a pump chamber ( 7 ). An impeller ( 3 ) is received so as to be rotatable inside the pump chamber ( 7 ). An inlet side channel ( 31 ) and an outlet side channel ( 33 ) are also formed inside the pump chamber ( 7 ). The impeller ( 7 ) has, in a blade region near the circumference thereof, a plurality of radially outward-extending blades ( 11 ). The inlet side channel ( 31 ) and the outlet side channel ( 33 ) run on opposite sides of the impeller ( 3 ) and both adjoin the impeller ( 3 ). The two side channels ( 31, 33 ) both extend in a partially annular shape along a flow path from an inlet channel to an outlet channel. The proposed side-channel pump is characterized in that the inlet side channel ( 31 ), averaged along the flow path, has a smaller cross-section than the outlet side channel ( 33 ). In this manner the impeller ( 3 ) can be maintained in a force equilibrium during operation. The friction between the impeller ( 3 ) and adjoining walls ( 19, 21 ) can be kept small and thereby wear phenomena can be kept small.

BACKGROUND OF THE INVENTION

The present invention relates to a side channel pump for delivering fluids. Furthermore, the invention relates to a fuel pump having a side channel pump of this type.

Fluids such as liquids and gases can be delivered and/or pressurized by way of different types of pumps. In motor vehicles, in particular, pumps are frequently used to deliver fuel from a tank to an internal combustion engine. For this purpose, the pump should have the capability of delivering fuel reliably and in a sufficient quantity under various ambient conditions. For example, the fuel should be capable of being delivered both in the case of a cold start and in the case of pronounced heating, in the case of which the formation of gas bubbles within the fuel can occur readily. Furthermore, the pump should have a long service life and should be capable of retaining its delivery properties reliably over a long service life of, for example, more than 10 years.

What are known as side channel pumps are therefore frequently used for delivering fuel in motor vehicles, since they are both robust during usage and can be manufactured and assembled inexpensively and simply. However, it has been observed that, in the case of conventional side channel pumps, a long service life is partially not achieved or that at least considerable wear phenomena occur over the service life of the pump.

DE 43 43 078 B4, U.S. Pat. No. 4,591,311 and DE 43 00 845 A1 describe conventional side channel pumps.

SUMMARY OF THE INVENTION

Embodiments of the present invention make it advantageously possible to increase the service life of a side channel pump or a fuel pump which is equipped with a side channel pump of this type and/or to keep wear phenomena low.

A side channel pump is proposed which has a housing which encloses a pump chamber. An impeller is accommodated within the pump chamber such that it can rotate. Furthermore, an inlet-side side channel and an outlet-side side channel are configured within the pump chamber. The housing has an inlet channel which opens into the inlet-side side channel and an outlet channel which leads away from the outlet-side side channel. The impeller has, in a blade region close to its outer circumference, a multiplicity of radially outwardly extending blades. The inlet-side side channel and the outlet-side side channel run on opposite sides of the impeller and both adjoin the impeller. The two side channels both extend along a flow path from the inlet channel in a partially annular manner to the outlet channel. The side channel pump which is proposed is distinguished by the fact that the inlet-side side channel has, averaged along the flow path, a smaller cross section than the outlet-side side channel.

The side channel pump which is proposed can be considered to be based on the findings and concepts which are explained in the following text.

In side channel pumps, a fluid to be delivered is sucked in through the inlet channel into the pump chamber. The impeller rotates in the pump chamber, for example driven by an electric motor. The blades of the impeller act on the fluid in such a way that parts of the fluid are carried along. Side channels are situated in a manner which is adjacent to the blades of the impeller on both opposite sides of the impeller. The inlet channel opens into the inlet-side side channel.

Since both side channels adjoin the impeller and are open toward the blades of the impeller, fluid which is sucked in through the inlet channel can firstly pass to the blades of the rotating impeller and can be carried along by the blades which move parallel to the side channels, and secondly a proportion of the fluid which is sucked in can also pass the blades and can pass between two adjacent blades toward the opposite outlet-side side channel. Here, the blades of the impeller interact with the fluid in such a way that the fluid is partially carried along in the rotational direction of the impeller and is partially pressed away from the impeller toward one of the side channels. As a result, after it has flowed through the inlet channel into the pump chamber, the fluid moves in a spiral manner along a flow path which leads from the inlet channel along the side channels toward the outlet channel. During this spiral movement, a considerable amount of energy is transmitted from the impeller to the fluid, with the result that the fluid can be delivered to the outlet channel and at the same time it can be pressurized and can then leave the pump chamber through the outlet channel.

It has now been observed that a force is exerted on the impeller by way of the intake of the fluid through the inlet channel, the throughflow of the fluid between the blades of the impeller and/or by way of the ejection of the fluid through the outlet channel, which force causes the impeller to be displaced in the direction toward the inlet side. On account of a force of this type, the impeller can rub on an inlet-side wall of the housing or, for example, of an intake cover during operation of the pump, which can lead to wear and to a considerable drop in the delivery capacity of the pump.

It has been recognized that the single-sided force loading of the impeller which has been observed can be avoided or at least reduced during operation of the pump by virtue of the fact that the two side channels are configured with different cross-sectional areas. Here, the cross section of the inlet-side side channel should have, averaged over the entire flow path, a smaller cross section than the outlet-side side channel. However, this does not rule out that the inlet-side side channel can have a larger cross section in small parts of the flow path, such as directly adjacently with respect to the inlet channel, than the opposite outlet-side side channel. However, the inlet-side side channel should have, over preferably considerably more than half the flow path, that is to say, for example, over at least 50%, preferably over at least 60% and, more preferably, over at least 75% of the flow path between the inlet channel and the outlet channel, a smaller cross section than the outlet-side side channel.

In other words, according to one embodiment of the invention, the inlet-side side channel has, at at least 60%, preferably at least 75% or 90% of the positions along the flow path, a smaller cross section than the outlet-side side channel at the same position along the flow path.

It has been recognized that, by way of an asymmetrical configuration of this type of the two side channels, a force can be brought about on the impeller, which force can counteract the otherwise observed force described further above and can compensate for said force at least partially. This can achieve a situation where the impeller is no longer pressed excessively toward the inlet side during operation, with the result that wear phenomena which are associated with this can be avoided or considerably reduced.

According to one embodiment, the inlet-side side channel has, at at least 50% of the positions along the flow path, a cross section which is smaller by between 5% and 30%, preferably between 10% and 25%, than the outlet-side side channel at the same position along the flow path. It has been observed that even minor asymmetries of this type with regard to the channel cross sections can lead to a considerable reduction of undesired forces on the impeller and therefore to reduced wear.

According to one embodiment, the inlet-side side channel has, at at least 50% of the positions along the flow path, a smaller depth than the outlet-side side channel at the same position along the flow path. In other words, the asymmetry of the cross sections of the side channels can be implemented mainly by way of a modification of the depths of the two side channels which is simple to implement. Here, the depths of the two side channels can differ from one another, for example, by between 5% and 30%, preferably between 10% and 25%.

It is noted that possible features and advantages of the invention are described herein in relation to different embodiments of the side channel pump. A person skilled in the art will recognize that features can be combined or replaced in a suitable way, in order for it to be possible in this way to arrive at further embodiments and possibly synergistic effects.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following text, embodiments of the invention will be described with reference to the appended drawings; neither the drawings nor the description are to be considered to restrict the invention, however. In the drawings:

FIG. 1 shows a perspective, partially cut-away view of a side channel pump.

FIG. 2 shows an exploded view of a pump part of a side channel pump.

FIG. 3 shows a plan view of a housing part of a side channel pump with a side channel which is configured therein.

FIG. 4 shows a greatly diagrammatic cross-sectional view through a pump chamber and adjoining housing parts of a conventional side channel pump.

FIG. 5 shows a greatly diagrammatic cross-sectional view through a pump chamber and adjoining housing parts of a side channel pump according to one embodiment of the present invention.

The figures are merely diagrammatic and are not true to scale. Identical or similar features are denoted in the figures by identical designations.

DETAILED DESCRIPTION

FIG. 1 shows the essential construction of a side channel pump 1. In the side channel pump 1, an impeller 3 which is in part also called an impeller wheel is accommodated within a pump chamber 7 which is enclosed by a housing 5. Close to its outer circumference 9, the impeller 3 has a multiplicity of blades 11 which run at least partially in the radial direction. Here, the impeller 3 can move rotationally within the pump chamber 7 and is set in rotation during operation of the pump 1, for example by an electric motor 13 which is coupled to the impeller 3 via a shaft 29. The housing 5 is configured in such a way that parts of the housing 5, which are also called the intake cover 15 and the intermediate housing 17, form walls 19, 21 which adjoin the end faces of the disk-shaped impeller 3 over predominant regions and are spaced apart from said end faces at any rate by a narrow gap 23.

During operation of the side channel pump 1, the impeller 3 is set in rotation by the electric motor 13 via a shaft 29 which is connected to said two components. By the blades 11 of the impeller 3 interacting with the fluid in the pump chamber 7, fuel, for example, coming from a tank via a line (not shown) is sucked into the pump chamber 7 through an inlet 25 which reaches through the housing 5. As a result of the rotation of the impeller 3 and the blades 11 which are arranged thereon, the fluid is pressurized, is conveyed through the pump chamber and is finally ejected through an outlet 27, for example, toward an internal combustion engine (not shown).

In the side channel pump 1 which is shown by way of example in FIG. 1, the impeller 3 is enclosed by the housing 5 and, in particular, by the intake cover 15 and the intermediate housing 17. As can be seen in the exploded view from FIG. 2, the impeller 3 is accommodated here within the space which is enclosed by the intake cover 15 and the intermediate housing 17. Furthermore, a free volume remains within said space, through which free volume a fluid can flow and which free volume is called a pump chamber 7. Here, the pump chamber 7 is formed by an inlet-side side channel 31 which is configured in the intake cover 15, an outlet-side side channel 33 which is configured in the intermediate housing 17, and a free volume between the blades 11 of the impeller 3. With the exception of the region of the pump chamber 7, walls 19, 21 of the intake cover 15 and the intermediate housing 17 adjoin corresponding end faces of the impeller 3 almost directly, said walls 19, 21 being spaced apart from said end faces at any rate by a narrow gap of, for example, 100 μm.

Fluid to be delivered comes from the inlet 25 and reaches the pump chamber 7 via an inlet channel 35 which opens into the inlet-side side channel 31. From there, the fluid is distributed over the pump chamber 7, that is to say also into regions between the blades 11 of the impeller 3 and into the opposite outlet-side side channel 33. Here, driven by the rotating impeller 3, it moves along a flow path 39 (see FIG. 3) which reaches from the inlet channel 35 as far as toward an outlet channel 37. Here, the fluid flows partially through the inlet-side side channel 31, partially through the outlet-side side channel 33 and is partially carried along by the blades 11 of the impeller. Here, the fluid circulates in a spiral movement between the individual part regions of the pump chamber 7. The fluid which is pressurized here leaves the pump chamber 7 through the outlet channel 37, flows through the electric motor 13 in the example which is shown in FIG. 1, and then leaves the housing 5 through the outlet 27.

As can be seen in the plan view from FIG. 3, the inlet-side side channel 31 which is configured in the intake cover 15 reaches from the inlet channel 35 in an annular manner along the flow path 39 in a part circle of approximately 300° as far as toward a region 41, at which, in the opposite intermediate housing 17, the outlet-side side channel 33 there leads into the outlet channel 37. Here, it passes a degassing bore 43.

FIG. 4 shows the configuration of an intake cover 15, an intermediate housing 17 and the impeller 3 which is accommodated therein for the case of a conventional side channel pump. FIG. 5 shows a corresponding configuration for a side channel pump according to one embodiment of the present invention.

In the conventional pump according to FIG. 4, the inlet-side side channel 31 and the outlet-side side channel 33 are dimensioned with identical widths B and identical depths KT1, KT2 and therefore have identical cross sections with an otherwise identical shape.

Although the two side channels 31, 33 are therefore of symmetrical configuration with regard to a plane through the center of the impeller 3, it has been observed that a force F₁ which is exerted on the impeller 3 on account of the pressure which is built up in the inlet-side side channel 31 is smaller than a force F₂ which is exerted on the impeller 3 in the opposite direction on account of the pressure which is built up in the outlet-side side channel 33. Since the two forces F₁, F₂ which are directed in opposite directions therefore compensate for one another only partially, a resulting force F₂-F₁ acts on the impeller 3, which force presses the impeller 3 toward the inlet-side intake cover 15. Here, the impeller 3 can come into mechanical contact with the intake cover 15, that is to say without a gap 23 which lies in between. Solid body friction can therefore occur between the impeller 3 and the intake cover 15, which solid body friction is substantially more pronounced than liquid friction, as occurs as long as the impeller 3 is spaced apart from the intake cover 15 via a gap 23 and the fluid to be delivered, that is to say low-viscosity fuel, for example, can flow through the gap.

In the side channel pump 1 according to one embodiment of the present invention, as shown in FIG. 5, although the inlet-side side channel 31 and the outlet-side side channel 33 are configured with identical widths B, they have different depths KT₁, KT₂. Their cross sections therefore differ and they are asymmetrical with regard to a plane which runs transversely with respect to the side channels 31, 33 and centrally through the impeller 3.

The channel depths KT₁, KT₂ can differ from one another, for example, by from 10% to 25%. For example, the two channel depths KT₁, KT₂ can lie in the range from 1 to 2 mm, but the channel depth KT₁ of the inlet-side side channel 31 can be smaller by from 0.1 to 0.2 mm than the channel depth KT₂ of the outlet-side side channel 33.

Instead of giving different dimensions only to the channel depths KT₁, KT₂ of the two side channels 31, 33, in principle as an alternative or in addition the width and/or shape of the side channels 31, 33 can also be selected to be different in such a way that the cross section of the inlet-side side channel 31 is somewhat smaller than that of the outlet-side side channel 33.

It has been observed that a relative reduction of this type in the cross section of the inlet-side side channel 31 can achieve a situation where the force F₁ which is exerted on the impeller 3 on account of the pressure which is built up in the inlet-side side channel 31 is approximately as great as a force F₂ which is exerted on the impeller 3 in the opposite direction on account of the pressure which is built up in the outlet-side side channel 33.

On account of the therefore equalized balance of forces on the impeller 3, the latter is no longer loaded or even displaced in the axial direction. Gaps 23 can therefore be ensured between both end faces and respectively adjoining walls 19, 21 of the intake cover 15 or the intermediate housing 17. The spacing which prevails in this way of the impeller 3 from the adjoining walls 19, 21 and the low liquid friction which prevails as a result between the end faces of the impeller 3 and said side walls 19, 21 can contribute to reduced wear phenomena and therefore to an increased service life of the side channel pump 1. 

1. A side channel pump (1), having: a housing (5) which encloses a pump chamber (7), an impeller (3) which is accommodated within the pump chamber (7) such that the impeller can rotate, and, within the pump chamber (7), an inlet-side side channel (31) and an outlet-side side channel (33); the housing (5) having an inlet channel (35) which opens into the inlet-side side channel (31) and an outlet channel (37) which leads away from the outlet-side side channel (33); the impeller (3) having, in a blade region close to an outer circumference (9) of the impeller, a multiplicity of radially outwardly extending blades (11), the inlet-side side channel (31) and the outlet-side side channel (33) running on opposite sides of the impeller (3) and adjoining the impeller (3), and the two side channels (31, 33) in each case extending along a flow path (39) from the inlet channel (35) in a partially annular manner to the outlet channel (37), characterized in that the inlet-side side channel (31) has, averaged along the flow path (39), a smaller cross section than the outlet-side side channel (33).
 2. The side channel pump as claimed in claim 1, the inlet-side side channel (31) having a smaller cross section at at least 50% of positions along the flow path (39) than the outlet-side side channel (33) at the same position along the flow path (39).
 3. The side channel pump as claimed in claim 1, the inlet-side side channel (31) having, at at least 50% of positions along the flow path (39), a cross section which is smaller by between 5% and 30% than the outlet-side side channel (33) at the same position along the flow path (39).
 4. The side channel pump as claimed in claim 1, the inlet-side side channel (31) having a smaller depth at at least 50% of the positions along the flow path (39) than the outlet-side side channel (33) at the same position along the flow path (39).
 5. The side channel pump as claimed in claim 4, the inlet-side side channel (31) having, at at least 50% of the positions along the flow path (39), a depth which is smaller by between 5% and 30% than the outlet-side side channel (33) at the same position along the flow path (39).
 6. A fuel pump for a motor vehicle, having a side channel pump (1) as claimed in claim
 1. 7. The side channel pump as claimed in claim 2, the inlet-side side channel (31) having, at at least 50% of the positions along the flow path (39), a cross section which is smaller by between 5% and 30% than the outlet-side side channel (33) at the same position along the flow path (39).
 8. The side channel pump as claimed in claim 7, the inlet-side side channel (31) having a smaller depth at at least 50% of the positions along the flow path (39) than the outlet-side side channel (33) at the same position along the flow path (39).
 9. The side channel pump as claimed in claim 8, the inlet-side side channel (31) having, at at least 50% of the positions along the flow path (39), a depth which is smaller by between 5% and 30% than the outlet-side side channel (33) at the same position along the flow path (39). 